int* findDisappearedNumbers(int* nums, int numsSize, int* returnSize) {
    int* res = malloc(numsSize * sizeof(int));
    int i, j = 0;
    for (i = 0; i < numsSize; i++)
    {
        res[i] = 0;
    }

    for (i = 0; i < numsSize; i++)
    {
        res[nums[i] - 1] += 1;
    }

    for (i = 0; i < numsSize; i++)
    {
        if (res[i] == 0)
            res[j++] = i + 1;
    }
    *returnSize = j;
    return res;

}